The present invention relates to a head-protection bag for vehicle occupants. More particularly, the invention relates to a bag which is inflated to expand over windows of doors and the B-pillar of the vehicle in the event of side collision or roll-over. In detail, the present invention relates to a head-protection bag for vehicle occupants comprising two sheets which are superposed on each other and interconnected by line-shaped connected portions and circular connected portions.
As one of the head-protection bag, there is a so-called xe2x80x9ccurtain bagxe2x80x9d which is inflated to expand over windows of doors and a B-pillar in the event of side collision or roll-over. In one such head-protection bag disclosed in Japanese Patent Unexamined Publication H10-291457, two sheets are superposed on each other and sewn together around their peripheries by seams of sewing yarn to form a chamber into which gas is supplied and filled.
To prevent the chamber from being inflated too thick, the two sheets are connected to each other by line-shaped connected portions. It has been found that stress concentration occurs at ends of the line-shaped connected portions. Thus, the ends of the connected portions are sewn into a circular form (circular connected portions) to disperse the stress. In this head-protection bag, large stress is applied to the seams on the circular connected portions. Therefore, it is an object of the present invention to provide a head-protection bag that absorbs the stress to be applied to the circular connected portions.
In addition, in this conventional design, air is sometimes entrapped in sealed portions of circular connected portions during the manufacturing process and thus increases the volume of a bag. The areas including the entrapped air can be stressed when the bag is folded. Therefore, it is another object of the present invention to provide a head-protection bag that does not include entrapped air.
A head-protection bag for vehicle occupants of the present invention is a bag which is disposed along a corner between a ceiling and a side of a vehicle cabin and is inflated with gas to expand downwardly along the side, comprises two sheets which are superposed on each other and are sewn together along their peripheries by line-shaped connected portions, and is characterized in that parts of the sheets are connected by circular connected portions; and that the circular connected portions are each formed at its center with an opening penetrating both of the sheets.
According to the aforementioned head-protection bag, when large stress is applied to the circular connected portions in the longitudinal direction of the bag during the inflation of the bag, areas including the circular connected portions are elongated in the direction of the stress because of the openings formed in the circular connected portions. Therefore, the stress to be applied to the circular connected portions can be absorbed.
As described above, conventionally, air is sometimes entrapped in sealed portions of circular connected portions during the manufacturing process and thus increases the volume of a bag. Also in this case, areas including the entrapped air can be stressed when the bag is folded. In the head-protection bag of the present invention, air can escape from sealed portions whereby no air is entrapped.
The present invention provides several alternatives for preventing gas from being entrapped in sealed portions. For example, when a sealing layer is formed between the sheets at the circular connected portion it may be bonded to the respective sheets. As a result, separation of the sealing layer from the sheets can be prevented because the stress is absorbed. In addition, when the sheets are connected by seams, the seams can be prevented from stretched, thus preventing gas from leaking through the stretched seams into the sealed portions.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.